The purpose built facility that was instrumental in developing models as diverse as the Holden Monaro, Torana and Commodore through to international models from Cadillac andChevrolet has been independently valued at about $20 million.

Although Holden has yet to reveal whether it will sell the entire facility or relocate any of the laboratories within the General Motors’ global empire, Peter Hay of leading property consultancy firm Hay Property Group estimates its value to be around $20m and says it will be an interesting property when it does hit the market.

“It would certainly have a higher value than rural land in the Gippsland region, but it is a very specialised property with unique facilities,” Hay told Fairfax Media.

“The very simple fact that it is a secret facility means we don’t exactly know what the facilities are on site, but it is easy to presume that it is of a very unique nature.”

He added that “it would require a specialised buyer” to take over the property as it stands, but also said the Lang Lang region is a “very popular area and it certainly has the potential to be sub-divided”.

One buyer likely to take a look at the property is trucking magnate Lindsay Fox, who as well as the massive Linfox trucking business also has one of the country’s most impressive car collections.

His transport company operates the largest privately-owned automotive test facility in Australia with its Australian Automotive Research Centre in Anglesea, 125km south-west ofMelbourne.

The facility is only half the size of Holden’s 2167-acre Lang Lang proving ground and, while offering an extensive network of varied road conditions, does not have the crash or emissions laboratories already housed within the Lang Lang facility.

Mr Fox also owns other unique and high profile properties, including the Phillip Island race track and Avalon airport.

Fairfax Media is awaiting an official comment from Mr Fox, but a spokesman for the Linfox Group indicated the company would be investigating the property when more details were available.The Holden Proving Ground, as it’s known, is south-east of Melbourne towards Phillip Island and was opened in 1957.

The Lang Lang facility has been developed over time into one of the most advanced facilities of its type in the southern hemisphere. Within its secured boundaries – which have regularly been pierced by photographers looking for scoop images - it has more than 44km of road systems, including a network of sealed tarmac and dirt roads to evaluate the comfort and handling of vehicles before they go on sale, rough roads to accelerate rattles and squeaks for long-term durability, mud and water baths to test the sealing properties of doors and windscreens as well as a circular banked track for high-speed driving.

In announcing it will stop building the Commodore and Cruze small car by 2017, Holden also announced it would wind down its engineering presence in Australia, putting hundreds of skilled engineers out of a job and the sale of many assets, including the proving ground.

Holden claims it is an “oasis of natural vegetation” and that around 75 per cent of it has been undeveloped leaving a “mixture of regenerated and undisturbed bushland habitat of high conservation significance.”

Holden says it also has “Australia’s most comprehensive safety test centre and a high-tech exhaust emission facility capable of conducting a wide range of vehicle exhaust emission tests to Australian, USA, European and other international requirements.”

Holden has confirmed it will only maintain a design studio at its Port Melbourne headquarters.

A spokeswoman indicated that the Lang Lang proving ground may be sold before the company winds down its manufacturing operations in 2017, as any future engineering and development work required for the locally-built Commodore and Cruze will be completed by at least 2016.

“There will naturally be some scaling back [of Holden’s engineering operations], but any of those details have yet to be decided,” said Holden’s Kate Lonsdale.

Arch rival Ford also has an advanced proving ground operation at the You Yangs, between Melbourne and Geelong.